1. Field of the Invention
The present invention relates to the field of medical instrumentation, specifically to the use of smart technology within miniature remote devices for the inspection, diagnosis, and treatment of internal organs of living organisms.
2. Description of Related Technology
Endoscopic and colonoscopic techniques are commonly used to inspect the accessible upper and lower portions, respectively, of the human gastrointestinal tract. A traditional endoscopic inspection of a human being (an example of which is the “EGD”) requires the patient to be partially or completely sedated while a long, thin, tubular probe is introduced into the esophagus, routed through the stomach, and ultimately into the upper portion of the small intestine (duodenum). This tubular probe typically contains a self-illuminating fiber optic cable and viewing device to allow visual inspection of tissue in the vicinity of the probe tip. See, for example, U.S. Pat. No. 3,901,220, “Endoscopes” issued Aug. 26, 1975. However, due to the tortuous path, fragility, small diameter, and length of the digestive tract, prior art endoscopic inspection such as the aforementioned EGD is limited to only the stomach and upper portions of the small intestine. See FIG. 1.
Similarly, traditional colonoscopic examination utilizes a thin, tubular fiber optic probe inserted into the large intestine (colon) via the rectum. Even the most penetrating colonoscopic inspections are limited to the colon and the terminal portion of the small intestine (ileum), due again primarily to the tortuosity and fragility of the large intestine and ileum. While a substantial number of diseases and conditions afflict the stomach, duodenum, colon, and ileum, several others may occur within the remaining, inaccessible portions of the gastrointestinal tract including the jejunum of the small intestine.
Both endoscopic and colonoscopic inspections further run a small but significant risk of physical damage to the patient, such as perforation of the duodenum or ileum, especially where disease has progressed to an advanced stage and the surrounding tissue has weakened or degenerated.
Alternatively, non-invasive diagnostic techniques such as X-ray inspection (e.g., so-called “upper-GI” and “lower-GI” series), which involves introducing barium or other contrast agents into the patient, are useful in identifying gross abnormalities, but require careful interpretation and are susceptible to misdiagnosis, shielding effects, and a plethora of other potential pitfalls. Furthermore, such techniques expose the patient to significant doses of ionizing X-ray radiation which ultimately may be deleterious to the patient's health.
The somewhat related technique of X-ray computed axial tomography (CAT) scanning provides information about the general condition of an individual's intestinal tract and internal organs, yet does not possess the necessary resolution to facilitate diagnosis of many types of conditions. It also suffers from the drawback of exposing the patient to substantial quantities of X-ray radiation. CAT scans of the GI tract also may require the use of ingested and/or intravenous contrast agents, the latter notably having a small but non-zero incidence of patient mortality. Furthermore, certain patients may not be given such contrast agents due to allergies or other pre-existing medical conditions, thereby substantially reducing the efficacy of the CAT scan as a diagnostic technique for these patients.
Magnetic resonance imaging (MRI) techniques, well known in the medical diagnostic arts, have certain benefits as compared to the aforementioned CAT scan, yet also suffer from limitations relating to resolution and interpretation of the resulting images, and in certain instances the required use of “contrast” agents. More recently, enhanced MRI techniques are being used to aid in the diagnosis and treatment of Crohn's disease, yet even these enhanced techniques suffer from limitations relating to resolution, especially when the disease has not progressed to more advanced stages.
Another related and well-known medical diagnostic technology is that of autofluorescence endoscopy. Simply stated, autofluorescence endoscopy uses a light source having specific characteristics (typically a coherent source such as a laser) to illuminate a portion of tissue under examination; the incident light excites electrons within the atoms of the tissue which ultimately produce a quantum transition therein resulting in an emission of electromagnetic radiation (fluorescence) from the tissue at one or more wavelengths. Additionally, so-called “remitted” energy, which is incident or excitation energy reflected or scattered from the tissue under analysis, is also produced. The fundamental principle behind the autofluorescence technique is that diseased or cancerous tissue has a different autofluorescence (and remitted light) spectrum than that associated with healthy tissue of similar composition; see FIG. 2. Generally speaking, diseased tissue autofluoresces to a lesser degree at a given wavelength under the same incident excitation radiation than healthy tissue. See, for example, U.S. Pat. No. 4,981,138, “Endoscopic Fiberoptic Fluorescence Spectrometer” issued Jan. 1, 1991. Unfortunately, however, the applicability of autofluorescence techniques has traditionally been limited to external areas of the body, or those accessible by endoscopic probe, thereby making this technique ineffective for diagnosing diseases of the central portion (jejunum) of the small intestine. See also U.S. Pat. No. 5,827,190, “Endoscope Having an Integrated CCD Sensor”.
In summary, endoscopic inspection is arguably the most efficient and effective prior art method of diagnosing conditions of the intestinal tract, especially those of a more chronic and insidious nature. However, due to its limited reach, endoscopic inspection is not an option for diagnosing or treating the central portions of the digestive tract, specifically the central region of the small intestine.
Delivery of Pharmaceutical or Other Agents
Oral administration is perhaps the most desirable approach for delivering an antigen or pharmaceutically active agent to a living subject. This approach, however, suffers from the significant disability relating to the generally poor uptake of antigens or pharmaceutically active agents by the intestinal tract. Some compounds are not suited for oral administration due to their poor penetration into the blood stream of the subject. Additionally, some orally administered agents may be destroyed through exposure to various substances present in the gastrointestinal system, such as proteolytic enzymes. The digestive process involves the physical and chemical breakdown of ingested food, followed by selective absorption of digested molecules in the intestine. Protease, lipases and other hydrolases secreted into the intestine effect the chemical breakdown of proteins, carbohydrates and other larger molecules present in food, and may also effect the operation or properties of administered agents.
So-called “controlled release” systems for delivery of agents have been developed to counter some of the foregoing problems with oral administration. Such systems are typically designed to administer drugs in specific areas of the body, such as the small intestine where absorption is comparatively good. In the intestinal tract it is critical that the agent not be carried beyond the site of delivery, or otherwise eliminated before it can exert pass into the bloodstream or exert the desired topical effect. In many cases, if a delivery vehicle can be made to couple itself to the lining of the appropriate viscus, its associated agent will be delivered to the targeted tissue, generally as a function of proximity and duration of the contact. Such functional relationship is especially true of radioisotopes.
Another current method of targeting drugs in the gastrointestinal tract involves the uncomfortable, time-consuming and often expensive method of intubation, in which a long, flexible tube containing the drug for delivery is literally snaked into the intestine of the subject.
Most pharmaceuticals or drugs are specific, in that they are recognized by key molecules which are involved in the disease. These drugs are then able to act directly on their relevant targets. For other diseases, such as cancer and inflammatory diseases, drug molecules are much less specific, and considerable often undesirable side effects are seen with these drugs. Hence, if these agents could be delivered to a specific location within the intestine, such diseases could potentially be treated more effectively with reduced side effects.
For tumorous tissue, it has been demonstrated that particles coated with a surfactant show prolonged circulation time after intravenous administration, and selectively accumulate in tumors because of comparatively high tumor vasculature leakage. These circulating surfactant-coated particles avoid rapid clearance by reticuloendothelial system. This technique of delivery to tumors is commonly referred to as “passive”.
Conversely, so-called “active” delivery is based on attachment of circulating particles to antibodies directed against antigens associated with the tumor vasculature. These antibodies (and other molecules, including short peptide sequences) can be used for targeting anti-cancer drugs in living subjects having tumorous tissue.
Receptors and Ligands
The interaction between a drug molecule and its receptor is often complex, and relates to the chemical mechanisms of drug action. Drug molecules attach (frequently in a reversible manner) to their receptors, not at a single site or by a single type of interaction, but rather in a variety of chemical modes with a number of complementary sites on the receptor molecule. Interactions that can be involved include relatively strong forces such as covalent bonding (comparatively rare), hydrogen bonding, or ion-ion interactions, and/or much weaker forces such as ion-dipole interactions, dipole-dipole interactions, charge-transfer complexation, van der Waals interactions, and hydrophobic bonding. The weaker attractive forces are often of most significance in drug-receptor interactions. Although individually weak, in the aggregate they provide a strong attachment of the drug to the receptor.
Most human immune system cells are white blood cells, of which there are many types. Lymphocytes are one type of white blood cell, and two major classes of lymphocytes are T cells and B cells. T cells are immune system cells that help to destroy infected cells, and coordinate the overall immune response. As is well known, the T cell includes a molecule on its surface known as the T-cell receptor. This receptor interacts with, inter alia, molecules called MHC (major histocompatibility complex). MHC molecules are disposed on the surfaces of many other cells of the body, and help the T cell to recognize antigen fragments present in its environment. B cells are best known for making antibodies which bind to an antigen, and marks the antigen for destruction by other immune system cells. In auto-immune dysfunction, the healthy, viable cells of the subject (as opposed to invading antigens) are marked for destruction. Hence, if receptor sites or antibody markers can be properly manipulated through the introduction of specially designed molecules (such as via the probe of the present invention), the defective auto-immune response may be at least partially blocked.
The gastrointestinal tract is lined with a single layer of epithelial cells (the mucosa, or epithelium). In the intestine, this layer protects a highly convoluted surface of projections into the lumen of the small intestine, and crypts, which penetrate into the underlying connective tissue. The epithelium is a particularly attractive site for certain types of therapy (e.g., gene therapy) because of its large mass of cells and its relative ease of access via the intestinal lumen. The lumenal surface of the epithelium interfaces with the external milieu, whereas its basolateral surface interfaces with the internal milieu. Hence, the epithelium may receive nucleic acids applied externally (via the lumen) and to direct the protein or peptide products to, inter alia, the luminal surface (such as for correcting a defect of digestion or absorption) or to the basolateral surface for secretion into the circulatory system (so as to act systemically).
The surface area of the intestinal epithelium is greatly increased by the presence of long, projections known as villi. Villi are microscopic, hairlike, thin-walled structures that contain many small blood vessels. There are large numbers of villi per square inch of intestine and, as a result, the total surface area of the inner wall of the small intestine is increased several hundred times. The physiological function of the villi is to facilitate absorption of dietary components that have hydrophilic and lipophilic properties that do not favor passive diffusion processes. Villi serve the same purpose in the case of negatively charged (drug) molecules: The large surface area created by the villi permits a large total absorption of hydrophilic molecules that have a poor diffusion tendency.
Additionally, the intestine has substantial length. This means there is a very large mass of tissue available for gene transfer. Moreover, the longitudinal character offers a high degree of precision with respect to the dosing of an introduced gene. The present invention provides a method for the in vivo targeting of the intestinal epithelium for the introduction of nucleic acids.
It has been known for some time that a number of specific uptake mechanisms exist in the intestinal tract for the intake of molecules. Thus, there are specific uptake mechanisms for a variety of different molecules. Most of these uptake mechanisms depend upon the presence of a specific protein or enzyme situated in the mucosal lamina which binds to the molecule and transports it into the cells lining and lamina. In certain cases, however, a specific binding protein is released into the intestine, which binds to its ligand in the lumen of the intestine. For example, during iron uptake in the intestine transferring is released from the stomach, binds to iron and is in turn bound by a receptor on the duodenal mucosa. The receptor-iron-iron complex is then taken up by receptor mediated endocytosis.
Despite the foregoing techniques, no existing prior art approach presently provides the ability to deliver pharmaceuticals, ligands, or other therapy agents directly to the central regions of the small intestine, without surgical intervention.
Tissue Ablation
Anatomical organs, such as the intestine, can develop a variety of abnormal conditions. It is known to treat such abnormal organ conditions in more severe cases by removal of the affected portion of the intestine. However, removal of even a portion of the intestine requires invasive surgery and general anesthesia, as well as a long recovery period. Other deleterious side effects (such as stomata) generally accompany such surgery, thus making such procedures highly undesirable from the perspective of the patient.
Alternatively, tissue may be ablated by heating the tissue (thermal ablation), freezing the tissue (cryogenic ablation), mechanically scraping or cutting of the tissue, or otherwise applying energy or manipulation of the tissue. The terms “ablating” and “ablation” as used herein broadly refer to the destruction, removal, or alteration, of tissue or the function of tissue, such as through cauterization, coagulation, scalloping, necrosing, removal, or the like. Ablation is most frequently accomplished by introducing an ablating member to an area or volume in proximity to the damaged tissue. Thermal ablation devices utilize a variety of ablation techniques including laser (i.e., coherent electromagnetic) energy, RF energy such a millimeter waves, radiation such as alpha and beta particles or gamma rays, an electrically resistive coil, or any other method of delivering energy.
Lasers are one of the most common devices used for surgical ablation. Lasers are inherently focused to a small area, However, laser energy (as well as other thermal and cryogenic devices) must be carefully applied and controlled to ensure that the abnormal tissue is ablated without damaging other normal tissue or organs in proximity to the target tissue.
Typically, large laser radiation sources, such as a Nd:YAG laser or a CO2 laser, have been coupled to a mobile hand-held device (“laser scalpel”) by means of fiber optic cabling. Thus, by correctly orientating the scalpel, the light generated by the laser generator is applied to the desired area. The use of such large lasers, however, suffers from several deficiencies. One such deficiency is size of the laser energy source, and the requirement that it be physically positioned within a fairly short distance from the scalpel so as to minimize problems with the fiber optic coupling. Additionally, such lasers inherently inefficient in comparison to semiconductor laser diodes.
Accordingly, most ablation techniques relating to intestinal tissue use endoscopes or other such devices to (i) inspect the condition of the tissue, and (ii) control the application of energy to the damaged tissue. However, as with other endoscopic techniques, ablation of the intestine is limited to those areas reasonably within reach of the endoscope. In cases where ablation of the central portion of the small intestine is required, the prior art provides no suitable approach short of invasive surgery.
Radiation Therapy
Typical prior art ionizing radiation treatment (such as for cancer or other malignant lesions) utilizes gamma or X-ray radiation to induce molecular-level damage within the cancerous or malignant tissue cell nuclei to ablate and effectively kill such cells and/or thwart their further reproduction. Existing radiation delivery systems include an external gamma/X-ray radiation source, or in certain cases, use of a radioisotope introduced by injection into the tissue or introduced intravenously, or other vehicle which is swallowed by or introduced endoscopically into the patient. However, these methods generally have the substantial drawback of indiscriminately irradiating mass amounts of undiseased tissue adjacent to the malignant cells. For example, the deposition profile of highly penetrating forms of radiation such as gamma or X-ray radiation (both forms of electromagnetic radiation with comparatively high frequencies, and hence energies) can not in many cases be accurately controlled within the human body; hence, there is significant collateral damage resulting from such external treatments to tissue and organs immediately in front of and behind the malignancy in the radiation line-of-sight. Hence, the use of gamma and/or X-ray radiation generally contributes significantly to whole body dose to the subject. Furthermore, gamma (and to a lesser degree X-ray) radiation is not easily collimated or laterally focused due to its highly penetrating nature, relating largely to its high energy photons. Such radiation exhibits a significant “tenth” thickness in most materials, even dense materials such as lead.
For a myriad of reasons including the increase likelihood of adhesions or perotineal cavity infection, it is also impractical and highly undesirable to surgically perforate the abdomen wall (via lapriscopy or other such techniques) in order to gain closer access to the intestine for radiation treatment. Esophogeal and rectal endoscopes of the type well known in the arts are useful in the localized inspection, biopsy, and treatment of accessible areas of the intestine, but again suffer from the inability to reach the central portions (majority) of the small intestine. Based on the foregoing, an improved method and apparatus for accurate, localized irradiation of the small intestine, including the interior regions thereof, is needed.
A more recent approach has been to use “targeted” delivery of radioisotopes to tumor sites or other areas of the intestine. See for example, U.S. Pat. No. 5,902,583 entitled “Genetic Induction of Receptors for Targeted Radiotherapy” issued May 11, 1999, wherein radio-labeled ligand localization comprising transducing the tumor with a gene encoding a membrane expressed protein unique to the tumor is described. Monoclonal antibodies directed to “tumor-associated” antigens on cancer cells, and radioactively labeled peptides able to bind to receptor positive tumor cells are also available. However, an improved method of administration and localized delivery of such radio-labeled ligands, especially to the epithelium of the intestine, is needed.
Ultrasound Imaging
Ultrasound imaging systems are commonplace in the prior art. During operation of these systems, ultrasonic signals, typically on the order of 250 kHz to 20 MHz, are transmitted into a subject's anatomy where they are absorbed, dispersed, refracted and reflected. The reflected ultrasound energy is received at a plurality of transducer elements which convert the reflected ultrasound energy back into electronic echo signals via the piezoelectric properties of the transducer. These received echo signals undergo a process known as beamforming; this process correlates the ultrasound signals into spatially coherent “beams.” Subsequently the processed signals are further analyzed to extract echo and Doppler shift information, and ultimately obtain an image of the subject's targeted anatomy (e.g., tissue, organs, vessels). Such images are represented in any number of common formats, including the so-called “B-mode.” A B-mode image is an image in which the brightness or luminosity of component pixels is adjusted in proportion to a corresponding echo signal strength or other measured parameter. The B-mode image represents a two dimensional cross-section of the subject's target area tissue through a transducer's scanning plane. The typical ultrasound B-mode image is formed by scanning the subject's target tissue in a predetermined pattern (e.g., linear, raster, conic, or sector scan) of the patient's target area by the transducer probe. The individual images produced by ultrasound imaging systems include discrete frames. Each frame has a limited field of view due to a relatively narrow region traversed by the transmitted ultrasound energy. As the transducer probe is manipulated along the patient's body surface, each previous image is replaced on the viewing display by a new image defined by the current position, and thus field of view, of the transducer probe. Interposed tissue (i.e., that between the organ of interest and the transducer(s)) also adds noise and “clutter” to both the transmitted and reflected signals, however, thereby reducing the accuracy of the system, and reducing the minimum spatial resolution of which the system is capable.
Based on the foregoing, it would be highly desirable to provide an apparatus and method by which treatment could be rendered remotely to various portions of the intestinal tract. More specifically, it would be highly desirable to provide an apparatus and method for, inter alia, (i) visual, autofluorescent, ultrasonic, or other types of inspection; (ii) delivery of medication, pharmaceuticals, radioisotopes, direct radiation; (iii) biopsy; (iv) physical expansion of constricted or scar tissues; (v) detection of the presence of one or more molecules present in vivo; and (vi) selective tissue ablation, in all portions of the interior of the digestive tract including the small intestine without invasive surgery or other extraordinary and potentially deleterious means.